Process for forming dye images

ABSTRACT

FORMAZAN DYE IMAGE DENSITIES FORMED BY TREATING A PHOTOGRAPHIC METAL IMAGE IN A HYDROPHILIC COLLOID BINDER LAY WITH A TETRAZOLIUM SALT SOLUTION IN THE PRESENCE OF A METAL COMPLEXING LIGAND ARE ENHANCED BY THE PRESENCE IN SAID BINDER LAYER OF AT LEAST ONE TERPOLYMER CONTAINING ABOUT 0.1% BY WEIGHT OF ACTIVE METHYLENE GROUPS IN ALIPHATIC SIDE CHAINS IN WHICH THE METHYLENE GROUPS ARE USUALLY SEPARATED FROM THE MAIN POLYMER CHAIN BY AT LEAST THREE CARBON ATOMS, THE TERPOLYMERS BEING FORMED OF AN ALKYL ACYLATE OR AN ALKYL METHACRYLATE AS ONE MONOMER, EITHER A SALT OF A SULFOALKYL ACRYLATE, A SALT OF A SULFOALKYL ALKACRYLATE, ACRYLIC ACID (OR SALT) OR AN ALKACRYLIC ACID (OR SALT) AS A SECOND MONOMER, AND EITHER A CYANOACETOXYALKYL ACRYLATE, A CYANOACETOXYALKY ALKACRYLATE, AN ACYL SUBSTITUTED ACETOXYALKYL ACRYLATE OR AN ACYL SUBSTITUTED ACETOXYALKYL ALKACRYLATE AS THE THIRD MONOMER.

United States Patent "ice Int. Cl. G03c 7/00 US. Cl. 9654 19 Claims ABSTRACT OF THE DISCLOSURE Formazan dye image densities formed by treating a photographic metal image in a hydrophilic colloid binder layer with a tetrazolium salt solution in the presence of a metal complexing ligand are enhanced by the presence in said binder layer of at least one terpolymer containing about 0.1% by weight of active methylene groups in aliphatic side chains in which the methylene groups are usually separated from the main polymer chain by at least three carbon atoms, the terpolymers being formed of an alkyl acylate or an alkyl methacrylate as one monomer, either a salt of a sulfoalkyl acrylate, a salt of a sulfoalkyl alkacrylate, acrylic acid (or salt) or an alkacrylic acid (or salt) as a second monomer, and either a cyanoacetoxyalkyl acrylate, a cyanoacetoxyalkyl alkacrylate, an acyl substituted acetoxyalkyl acrylate or an acyl substituted acetoxyalkyl alkacrylate as the third monomer.

This invention is related to photography, photographic elements, compositions for use in photographic processing and photographic processes for forming high density dye images from photographic metal images.

In photography, it is sometimes desired to convert a photographic metal image into a dye image or to add to a photographic silver image a corresponding dye image. Processes are desired that will make it possible to obtain photographic reproductions having good image densities with elements containing less silver than usual or with photographic silver images having lower image densities than needed. If a dye image alone is desired, it is necessary to provide a convenient method for removing the metallic image.

Processes have been described in British Pat. 908,299 in which a silver image in a photographic emulsion layer is converted into a formazan dye image by treating the silver image with a tetrazolium salt in the presence of cyanide ions and, subsequently, bleaching the image with a ferricyanide bromide bleach bath, followed by washing, fixing with a sodium thiosulfate bath, washing and drying. It is desired to prepare higher density dye images from metal images than is possible from the prior art processes.

It is, therefore, an object of our invention to provide a novel process for converting a novel photographic metal image in the presence of a certain polymeric colloids into a higher density dye image than is possible with the prior art processes and preferably without using cyanide ions and without a separate bleach step and a separate fixing step.

Another object of our invention is to provide a novel, single-step process for converting a metal image to a high density formazan dye image and, simultaneously, to remove the metal image from a black-and-white developed photographic element.

Still another object of our invention is to provide a novel method which is valuable for the conversion of even a low density silver image into a formazan dye 3,671,244 Patented June 20, 1972 image of a density higher than previously realized with the same dyes.

Still another object of our invention is to enhance an image or improve the image contrast obtainable from a silver image alone, by the use of high density formazan dye images.

Still other objects of our invention will become ap parent from a consideration of the following specification and claims.

These and still other objects of our invention are accomplished by our novel process in which a photographic element containing at least one terpolymer and a metal image with a standard oxidation potential more positive than --0.98 volt is brought into contact with an aqueous solution of a tetrazolium salt (T-salt) until the T-salt oxidizes the metal image to a metal ion and the T-salt is reduced to the corresponding formazan dye in situ. The T-salt is used in the presence of a metal complexing ligand that forms a metal complex. This metal complexing ligand is either 1) a separate compound in the T-salt solution or (2) a moiety of the T-salt molecule, or the complexing function is filled by a combination of 1) and (2). The formazan dye which is produced from the T-salt is nondiffusible and replaces at least a portion of the metal image.

The formazan dye image formed remains at the site of the original zero valent metal image that has been converted to a metal ion. The metal ion is complexed as part of the formazan dye when the T-salt (and formazan dye formed from it) contains a moiety that is a metal ion complexing agent, or the metal ion is removed by a fixing step or the use of a complexing agent which renders the metal ion soluble and which is present in the T-salt solution. Alternatively, the metal ion is reconverted to the zero valent metal image by a subsequent reduction step so the formazan dye image formed previously is supplemented by a metallic image.

Our invention is characterized by forming an insoluble formazan dye image at the site of a zero valent metal image in a hydrophilic colloid binder and in the presence of at least one terpolymer that contains at least about 0.1%, by weight, of active methylene groups in aliphatic side chains which contain at least three carbon atoms separating said active methylene groups from the main polymer chain of said terpolymer. The presence of our terpolymer which is either a solution terpolymer or a latex terpolymer, in the binder produces a valuable increase in the formazan dye image density, especially in the D that is obtained from a given zero valent metal image density. The zero valent metal image is advantageously formed in any photographic element containing an appropriate light-sensitive metal salt prepared in a hydrophilic colloid binder that contains one of our synthetic terpolymers.

In accordance with our invention, we have found that the above objects are accomplished by forming formazan dye images in hydrophilic colloid layers from metal images in the presence of at least one terpolymer containing at least about 0.1%, by weight, of active methylene groups in aliphatic side chains. Terpolymers used to advantage are prepared from acrylic-type esters having active methylene groups in the ester moiety or in a substituent alpha to the carbonyl group. Such compounds can be represented by the formula:

c Hg=?(%0 R,

where R is hydrogen, alkyl or where R is alkylene and X is aliphatic acyl or cyano and R is alkyl, cycloalkyl, aryl or i -R,OCCH2X where R and X are as defined, provided that one and only one of R and R is always The acrylic ester monomers containing the active methylene groups can be reacted with like monomers or with at least one other ethylenically unsaturated monomer to form a polymeric substance. The polymers employed in photographic materials according to the practice of this invention are addition terpolymers containing at least about 0.1%, generally about 0.1 to about 1.4%, by weight, of active methylene groups in aliphatic side chains of the terpolymers. Active methylene groups are methylene groups between two activating groups, for example, electronegative groups such as carbonyl. Such methylene groups exhibit unusual chemical activity and are said to be active. Malonic esters, acetoacetic esters, cyanoacetic esters and 1,3-diketones are examples of compounds containing such groups. The active methylene groups are usually separated from the main polymer chain by at least three carbon atoms and can be introduced into the side chains of a terpolymer by copolymerizing a monomer containing at least one active methylene group, for example, a

group, and an independently polymerizable unsaturated methylene group with at least one other copolymerizable monomer containing, for example, at least one 01' CHz=C group. Where reference is made to the fact that the active methylene groups are in aliphatic side chains of the terpolymers, this is intended to mean that the chain which links the active methylene group to the main polymer chain of the terpolymer is free of non-aliphatic groups, e.g., aromatic groups, i.e., the active methylene group is bonded to the main chain or backbone of the terpolymer through an aliphatic linkage. The molecular weights of the polymers employed in photographic emulsions and elements according to the practice of this invention are subject to wide variation, but are often in the range of about 5,000 to about 500,000.

Particularly useful terpolymers are prepared by terpolymerizing at least one unsaturated polymerizable compound containing one or more groups with a different monomer having the formula:

CHz=C( J-OR,.

where R and R are as defined hereinbefore. Useful terpolymers comprise at least one unit of a monomer having the above formula with at least one other ethylenically unsaturated polymerizable monomer which forms addition polymers, such as vinyl esters, amides, nitriles, ketones, halides, ethers, alpha-beta-unsaturated acids or esters thereof, olefins, diolefins and the like, as exemplified by acrylonitrile, methacrylonitrile, styrene, alphamethylstyrene, acrylamide, vinyl chloride, methyl vinyl ketone, fumaric, maleic and itaconic esters, Z-chloroethyl vinyl ether, acrylic acid, sodium methacryloyloxyethyl sulfate, methacrylic acid, difnethylaminoethyl methacrylate, 4,4,9-trimethyl-8-oxo-7-QXa-4-azonia 9 decene 1 sulwhere R is hydrogen or methyl; and R is alkyl, desirably containing up to about 10 carbon atoms, as exemplified by methyl, propyl, isobutyl, octyl, decyl and the like, (B) about 3 to about 30%, by weight, of a sulfoester monomer (2) having the formula:

where R is hydrogen or alkyl, desirably containing up to about 12 carbon atoms, often 1-8 carbon atoms, as exemplified by methyl, pentyl, octyl, dodecyl and the like; R has its valence bonds on different carbon atoms of any divalent hydrocarbon radical (saturated or unsaturated) generally containing up to 12 carbon atoms, e.g., any aliphatic radical (e.g., ethylene, 1,3-propylene, 1,2- propylene, tetramethylene, 1,3-isobutylene, 2-butylene, butyrylene, pentamethylene, hexamethylene, octamethylene etc.), any cycloaliphatic radical (e.g., cyclopentyl, cyclohexyl, etc.), any aromatic radical (e.g., phenylene, bisphenylene, naphthylene, etc.) or any divalent aliphatic hydrocarbon, preferably saturated, in which a chain of carbon atoms joining the oxygen and sulfur atoms in Formula III is interrupted by an atom from Group VIa of the Periodic Table having an atomic weight of less than about 33, Le, at least one -O and/or -S- radical interrupts the carbon chains and M is a cation, e.g., hydrogen, an alkali metal (e.g., sodium, potassium, etc.), ammonium, a water-soluble organic amine having an ionizable proton on a nitrogen atom (e.g., a cation of triethyl amine, diethanol amine, etc.); and (C) about 2 to about 20%, by Weight, of a monomer (3) having the formula:

where R; is hydrogen, alkyl, desirably containing up to 12 carbon atoms as exemplified by methyl, n-butyl, octyl, dodecyl and the like, or

12 carbon atoms, as exemplified by phenyl and the like or where R and X are as defined hereinbefore for this radical, provided that one and only one of R and R is always 0 'REOJ:LCHZX where R and X are as defined previously; and solution terpolymers containing A and C as described above for the latex terpolymer but B is about 3 to about 30% by weight of an acrylic acid (or salts) having the formula:

where R is hydrogen or alkyl as defined previously and M is a cation as described previously.

The preferred latex terpolymers Containing sulfoester units contain in polymerized form at least about 65% by weight of monomer (1), at least about 3% by weight of sulfoester monomer (2) and at least 2% by weight of monomer (3). The preferred solution terpolymers containing acrylic acid units contain in polymerized form, at least 65% by weight of monomer (l), at least about 10% by weight of acrylic acid and at least about 2% by weight of monomer (3).

The ethylenically unsaturated polymerizable monomers having Formula I are prepared using any procedure suitable for this purpose. In general, the reaction of acid chlorides, acid anhydrides or mixed anhydrides containing active methylene groups with acrylic esters containing hydroxyalkyl substituents are employed. A preferred synthesis for preparing the esters having an active methylene group in the ester moiety involves the reaction of a hydroxyalkyl ester of acrylic or an alpha-alkyl acrylic acid with diketene or cyanoacetyl chloride. The esters having active methylene groups in the alpha-substituent in the above formula can be obtained by reacting the alphahydroxyalkyl substituted acrylic esters with diketene or cyanoacetyl chloride. Such reactions are not particularly pressure sensitive and, therefore, can be carried out at atmospheric, superatmospheric or subatmospheric pressure. The temperature range is subject to wide variation depending, for example, upon the particular reactants employed, solvents and like considerations, but generally temperatures up to about 100 C. and often temperatures in the range of about 35 to about 100 C. are suitable. The reaction is advantageously carried out in the absence of solvent or using a suitable vehicle, for example, diethyl ether, ethyl acetate or the like and is generally completed in less than twenty hours, often less than four hours. The acrylic esters containing the active methylene groups are generally viscous liquids or oils and can be separated from the reaction medium by any means suitable for this purpose, for example, by distillation.

The other monomers are well known and need not be discussed further. Our terpolymers are prepared and incorporated in our silver halide emulsion layers as is described in Smith, US. Pat. 3,488,708, issued Jan. 6, 1970, particularly as described in column 6, line 20 through column 8, line 54, this material being incorporated herein by reference.

Typical terpolymers used to advantage according to our invention include the following:

(1) Terpoly(butyl acrylate-sodium 3-sulfopropyl acrylate-acetoacetoxyethyl-methacrylate) 80: 10: 10% by weight (2) Terpoly(butyl acrylate-sodium 3-sulfopropyl acrylate acetoacetoxyethyl methacrylate) 90: 3 :7% by weight (3) Terpoly(butyl acrylate-sodium 3-sulfopropyl acrylate acetoacetoxyethyl methacrylate), 91 ::4% by weight (4) Terpoly(butyl methacrylate-sodium 3 -sulfopropyl acrylate-acetoacetoxyethyl methacrylate) 82: 8% by weight (5) Terpoly(butyl methacrylate-sodium 3-sulfopropyl acrylate-acetoacetoxyethyl methacrylate), 89:4:7% by weight (6) Terpoly(butyl methacrylate-sodium 3-sul-fopropyl acrylate-acetoacetoxyethyl methacrylate), 90:8:2% by weight (7) Terpoly(methyl acrylate-sodium 3-sulfopropyl acrylate-acetoacetoxyethyl methacrylate), 80:10:10% by weight erpoly(methyl acrylate-sodium 3-sulfopropyl acrylate-acetoacetoxyethyl methacrylate), 89:5 :6% .by weight (9) Terpoly(methyl acrylate-sodium 3-Sulfopr0py1 acrylate-acetoacetoxyethyl methacrylate), 92:6:2% by weight (10) Terpoly(ethyl acrylate-acrylic acid-acetoacetoxyethyl methacrylate), 82:10:8% 'by Weight (11) Terpoly(ethyl acrylate-acrylic acid-acetoacetoxyethyl methacrylate), 72:24:4% by weight (12) Terpoly(ethyl acrylate acrylic acid acetoacetoxyethyl methacrylate), 90:8:2% by weight (13) Terpoly(nonyl acrylate-sodium 2-sulfoethyl acrylate-acetoacetoxyethyl methacrylate), 90:5:5% by weight (14) Terpoly(nonyl acrylate-sodium 2-sulfoethyl acrylate-acetoacetoxyethyl methacrylate), :10:10% by weight (15) Terpoly(methyl methacrylate-sodium Z-sulfoethyl methacrylate-acetoacetoxypropyl acrylate), 90:3 :7% by weight (16) Terpoly(methyl methacrylate-sodium 2-sulfoethyl methacrylate-acetoacetoxypropyl acrylate) 90: 8 22% by weight (17) Terpoly(ethyl acrylate-sodium 4-sulfobutyl methacrylate-acetoacetoxyethyl acrylate), 90:3:7% by Weight (18) Terpoly(ethyl acrylate-sodium 4-sulfobutyl methacrylate-acetoacetoxyethyl acrylate), :8:7% by weight (19) Terpoly(butyl acrylate-acrylic acid-acetoacetoxypropyl methacrylate), :3:7% by Weight (20) Terpoly(butyl acrylate-acrylic acid-acetoacetoxypropyl methacrylate), 91 :5 :4% by weight (21) Terpoly(methyl acrylate-sodium 3-su1fopropyl acrylate-ethyl-a-acetoacetoxymethyl acrylate), 89:5:6% by weight (22) Terpoly(methyl acrylate-acrylic acld-ethyl tat-acetoacetoxypropyl acrylate), 91:5:4% by Weight (23) Terpoly(methyl acrylate-sodium 3-sulfopropyl acrylate-cyanoacetoxyethyl methacrylate), 89:5:6% by weight Our terpolymers are used in the range of from about 1% to about 85%, by weight, of the binder, e.g., hydrophilic colloid plus terpolymer for the metal image in our elements with a preferred range of from about 20% to about 60% by weight.

The metal images, e.g., images made of palladium or any metal more easily oxidized (i.e., has a standard oxidation potential more positive than -0.98 volt) (e.g., silver, nickel, copper, iron, palladium, zinc, lead, tin, etc.) in hydrophilic colloid layers containing one or more ot our terpolymers are used to advantage in the preparation of our high density formazan dye images. The metal images are produced in the presence of our terpolymers by any conventional image-forming methods and especially by photographic methods using chemical or physical developing-out photographic elements and processes.

Silver images, for example, are produced advantageously by developing latent images in lightsensitive silver salt dispersons in a photographic hydrophilic COllOld emulsion in the presence of our terpolymers. Any of the silver halide emulsions, e.g., silver chloride, silver bromide, silver iodide, silver chlorobromide, silver bromoiodide, silver chlorobromoiodide, etc., as well as other light-sensitive silver salts dispersed in gelatin or gelatin substitute and always in the presence of our terpolymer(s) are used to advantage. These emulsions are advantageously coated on any of the usual supports, including paper, glass, polymeric films, e.g., cellulose acetate film, polyvinyl acetal film, polystyrene film, polypropylene film and other polyolefin films, polycarbonate film, polyethylene terephthalate film and other polyester films. Latent images produced by the usual image-exposure techniques are advantageously developed to silver images by treating with an aqueous alkaline solution of a developing agent such as a hydroquinone, a catechol, a pyrogallol, an aminoand wherein R and R each represent a group such as an aryl group, e.g., a phenyl group (e.g., phenyl, tolyl, butylphenyl, a hydroxyphenyl group, an alkali metal or ammonium salt of carboxyphenyl, a carboxyphenyl group, an ethoxycarbonylphenyl group, an aminophenyl group, a carbamylphenyl group, a sulfophenyl group, an alkali metal or ammonium salt of a sulfophenyl group, a sulfonamidophenyl group, a sulfamylphenyl group, a mercaptophenyl group, a nitrophenyl group, etc.), a naphthyl group (e.g., a-naphthyl, fl-naphthyl, a carboxynaphthyl group, a hydroxynaphthyl group, a sulfonaphthyl group, a mercaptonaphthyl group, an aminonaphthyl group, a carbamylnaphthyl group, a sulfonamidonaphthyl group, a sulfamylnaphthyl group, a nitronaphthyl group, etc.) etc., and a heterocyclic group, preferably containing from to 6 atoms, and preferably containing hetero atoms, such as nitrogen, sulphur, oxygen and selenium, such as, for example, a thiazolyl group, a benzothiazolyl group, an oxazolyl group, a benzoxazolyl group, a selenazolyl group, a benzoselenazolyl group, a benzirnidazolyl group, a naphthimidazolyl group, a triazinyl group, a pyridiminyl group, a pyridyl group, a quinolyl group, a thienyl group, etc.; R represents any of the groups represented by R and, in addition, represents an alkyl group (e.g., methyl, butyl, hexyl, dodecyl, mercaptomethyl, mercaptoethyl, etc.) etc., hydrogen, hydroxyl, carboxyl, a salt of a carboxyl group (e.g., an alkali metal salt or ammonium salt), a carboxy ester group (e.g., methoxycarbonyl, ethoxycarbonyl, phenoxycarbonyl, etc.), an amino group (e.g., amino, ethylamino, dimethylamino, anilino, etc.), a carbamyl group (e.g., carbamyl, ethylcarbamyl, dimethylcarbamyl, phenylcarbamyl, etc.), sulfo, a salt of a sulfo group (e.g., an alkali metal salt), a sulfoamido group (e.g., methylsulfonamido, butylsulfonamido, phenylsulfonamido, etc.), a sulfamyl group (e.g., sulfamyl, methylsulfarnyl, butyl sulfamyl, phenylsulfamyl, etc.), the mercapto group, the nitro group, or any other substituent cited as being present in this position of the formazan or the tetrazolium salt in Chem. Rev. 55, 355- 483 (1955); and the substituents R and R advantageously contain an electron-sharing group capable of forming metal chelates or complexes, such as primary, secondary and tertiary amino, substituted amino, oxime, thioether, keto, thioketo, hydroxyl, mercapto, carboxyl, sulfo,

phospho, alkoxy groups or complexes; X" represents an anion (e.g., chloride, iodide, bromide, thiocyanate, thiosulfate, sulfate, paratoluenesulfonate, me'thylsulfate, ethylsulfate, nitrate, acetate, perchlorate, perborate, sulfite, hydroxide, carbonate, etc.), D represents a divalent aromatic group (e.g., a phenylene, diphenylene, naphthalene, phenylmethylphenyl, etc.); and E represents a divalent group such as an alkylene group (e.g., methylene, ethylene, propylene, butylene, etc.), an arylene group (e.g., phenylene naphthalene, diphenylene, etc.), an arylene alkylene group, for example, a phenylene alkylene group e.g., phenylene methyelne, phenylene butylene, phenylene hexylene, etc.) a naphthylene alkylene group (e.g., naphthylene methylene, naphthylene butylene, naphthylene propylene, etc.), etc.; It represents an integer of from 1 to 5. Solutions of T-salts in which at least one of R R and R represents a thiazolyl nucleus, a benzothiazolyl nucleus, a naphthothiazolyl nucleus, a benzimidazolyl nucleus, a naphthimidazolyl nucleus, or a pyridyl nucleus and/or X" represents a chloride ion, a bromide ion, an iodide ion, a thiocyanate ion or a thiosulfate ion do not require a separate metal ion complexing agent for use in converting our metal images to formazan dye images; however, a separate complexing agent is used if additional complexing activity is desired.

Tetrazolium salts used to advantage according to our invention include the following representative compounds: T-salt No.: T-Salt name 1 2- (benzolthiazol-Z-yl -3-phenyl-5- (o-chlorophenyl)-2H-tetrazoliurn chloride 2 2-(4,5-dimethylthiazol-2-yl)-3,5-dipheny1-2H- tetrazolium bromide 3 3,5-diphenyl-2-(4-phenylthiaZol-2-yl)-2H- tetazolium iodide 5-(4,5-dimethylthiazol-2-yl)-2,3-diphenyl-2I-I- tetrazolium chloride 2- (benzothiazol-Z-yl) -3-phenyl-5-(thien-2-y1) -2H- tetrazolium chloride 2,3-diphenyl-5- (pyrid-Z-yl)-2H-tetrazolium bromide 2,3-diphenyl-5-(pyrid-4-yl)-2H-tetrazolium chloride 2,5 -diphenyl-3- pyrid-3-yl) -2H-tetrazolium chloride 2-(4-chlorophenyl)-3-(2-chlorophenyD-S-pyrid- 2yl)-2H-tetrazolium iodide 2,3-diphenyl-5-(benzimidazol-Z-yl)-2H-tetrazolium chloride 2, 3-di (4-bromophenyl -5 (benzothiazol-Z-yl) ZH-tetrazolium chloride 2- (benzothiazol-Z-yl -3-phenyl-5- (2-phenyltriazol- 5-yl)-2H-tetrazolium chloride 2,2'-di (benzothiazol-Z-yl) -3,3 -diphenyl-5 ,5

diethylene di-(-2-'H-tetrazolium chloride) 2,2-di(benzothiazol-Z-yl)-3,3'-diphenyl-5,5'-di- 1,6-hexylene di-(ZH-tetrazolium chloride) 2,2-di thiazol-2-yl -3 ,3 '-diphenyl-5 ,5 '-dipheny1- ene-di(2H-tetrazolium iodide) 5,5'-di-(thiazol-2-yl)-3,3'-diphenyl-2,2-di-pdiphenylene di-(ZH-tetrazolium chloride) 3,3'-di(thiazol-2-yl)-5,5'-di(thien-2-yl)-2,2'-di-p- (3,3'-di-methoxy-diphenylene) di-(ZH-tetrazolium chloride) 3,3,5,5'-tetraphenyl-2,2'-syn-p-phenylthiourea di-(ZH-tetrazolium bromide) 2,2,3,3 '-tetra( pyrid-Z-yl) -5 ,5 '-p-phenylene ethylene di-(ZH-tetrazolium chloride) 2- (benzothi azol-Z-yl) -5- (4-acetarnidophenyl) -3- (4-phenylazophenyl)-2H-tetrazolium bromide 2- (benzothiazol-Z-yl -3- (4-methoxyphenyl -5- phenyI-ZH-tetrazolium bromide 2- 4,5 -dimethylthiazol-2-yl) -3 ,5 -diphenyl-2H- tetrazolium bromide 2- 4-chlorophenyl) -3- 2-chlorophenyl) -5- (pyrid- 2-yl)-2H-tetrazolium iodide 2-(benzimidazol-2-yl)-5-(2-chlorophenyl)-3-phenyl- 2H-tetrazolium chloride 114 3,3,5,5'-tetraphenyl-2,2-di-p-(3,3'-dimethyldiphenylene di-(ZH-tetrazolium chloride) 1 l 3,3 ,5 ,5 '-tetraphenyl-2,2'-syn-p-phenylthiourea di-(ZH-tetrazolium chloride) 116 3,3,5,5'-tetraphenyl-2,2'-syn-p-phenyl sulfoxide di-(ZH-tetrazolium chloride) 117 2,2,3,3-tetraphenyl-5,5'-phenylene ethylene di- (ZH-tetrazolium chloride) These tetrazolium salts are well known in the art, most of them having been described in literature references such as Chemical Revue 55, published bi-monthly for the American Chemical Society by the Williams and Wilkins Co., Baltimore, 1955. Any tetrazolium salts that are not shown specifically in the prior art are advantageously prepared by methods well known in the art.

When aqueous solutions of our T-salts are brought into contact with metal images of palladium or any metal more easily oxidized (i.e., has a standard oxidation potential more positive than -0.98 volt) (e.g., silver, nickel, copper, iron, palladium, zinc, lead, tin, etc.), the metal is oxidized to its ion and the T-salt is reduced to produce the corresponding formazan dye. The following equation shows a typical reaction:

C C it. 1'.

T-salt Formazan Dye Any liquid that is a silver complexing agent is advantageously used that produces a silver ion complex.

Included among the ligands used to advantage are the following typical examples: water-soluble thiosulfates (e.g., sodium thiosulfate, potassium thiosulfate, ammonium thiosulfate, etc.), thiourea, ethylenethiourea, a water-soluble thiocyanate (e.g., sodium thiocyanate, potassium thiocyanate, ammonium thiocyanate), a water-soluble sulfur containing dibasic acid. Water-soluble diols used to advantage include those having the formula:

wherein p is an integer of from 2 to 13; the Zs represent oxygen or sulfur atoms such that at least one-third of the Z atoms are sulfur and there are at least two consecutive Zs in the structure of the compound which are sulfur atoms. The diols advantageously used are also included in compounds having the formula:

wherein X and X represent oxygen or sulfur, such that when X represents oxygen, X represents sulfur and when X represents sulfur, X represents oxygen; 0, d, e, f and g each represent an integer of from 1 to 15, such that the sum of c+d+e+f+g represents an integer of from 6 to to 19, and such that at least one third of the total of all the Xs plus all the X s represent sulfur atoms and at least two consecutive Xs and/or X s in the structure of the compound are sulfur atoms.

Typical diols include the following: 1) 3,6-dithia-1,8-octanediol HOCH CH SCH CH SCH CH OH (2) 3,6,9-trithia-l,ll-undecanediol H0CH CH SCH CH SCH CH SCH CH OH (3) 3,6,9,12-tetrathia-1,l4-tetradecanediol HO(CH CH S) CH CH OH 12 (4) 9-oxa-3,6,9,12,IS-tetrathia-1,17-heptadecanediol HO (CH CH S) CH CH O (CH CH S CH CH OH 5) 9,12-dioxa-3,6,15,18-tetrathia-1,20-eicosanediol HO (CH CI-I S) CH CH O) 2 (CH CH S CH CH 0H (6) 3,6-dioxa-9,l2-dithia-l,14-tetradecanediol HO (CH CH O) 2 (CH CH S CH CH OH (7) 3 12-dioxa-6,9-dithia-1,14-tetradecanediol HOCH CH O CH CH S) CH CH OCH CH OH (8) 3,1 8-dioxa-6,9, 12, 1S-tetrathia-1,20-eicosanediol HOCH CH O CH CH S CH CH OCH CH OH ('9) 12,18-dioxa-3,6,9,15,21,24,27-heptathia-1,29-nonacosanediol (10) 6,9, 15,18-tetrathia-3,12,2l-trioxa-1,23-tricosanedio1 Water-soluble sulfur containing dibasic acids used to advantage include those having the formula:

HOOCCH (SCH CH SCH COOH in which q represents an integer of from 1 to, and including, 3 and the alkali metal and ammonium salts of said acids. Typical illustrative examples include:

ethylenebis-thioglycolic acid HOOCCHgSCHgCHgSCHQCOOH 3,6,9-trithiahendecanedioic acid HOOCCH (SCH CH SCH COOH 3,6,9,1Z-tetrathiatetradecanedioic acid HOOCCH (SCH CH SCH CO0H ethylene-bis-thioglycolic acid di-sodium salt ethylene-bis-thioglycolic acid di-potassium salt ethylene-bis-thioglycolic acid di-ammonium salt 3,6,9-trithiahendecanedioic acid di-sodium salt 1 3,6,9,12-tetrathiatetradecanedioic acid di-sodium salt The concentration of the T-salt and the ligand in our compositions can be varied considerably, with an operable range of concentrations extending from the solubility limit of the T-salt and the solubility limit of the ligand down to a minimum concentration where the overall reaction potential for the specific T-salt, ligand and specific metal image just remains positive, usually above +0.01 volt. The operable concentration ranges and the preferred concentration ranges are readily determined by methods well known in the art and need not be discussed further.

The following examples are included for a further understanding of our invention: 4

EXAMPLE 1 Three photographic X-ray elements, W (outside our invention), A and B (both of our invention) are prepared by coating silver bromoiodide emulsions on both sides of a transparent support with emulsion W on both sides of element W, emulsion A on both sides of element A, and emulsion B on both sides of element B. Each of the emulsion layers have the same silver bromoiodide coated at 175 mg./ ft. of silver and 144 nag/ft. of the binder indicated in Table I. The elements are each given the same sensitometric exposure, black-and-white processed in a conventional aqueous alkaline hydroquinone p-methylaminophenol developing solution, fixed in a conventional alkali metal thiosulfate fixing bath, washed and dried. The D,,,,,,; of the resulting silver image is measured, then the silver images are treated for 60 seconds at F. in T- salt Solution 1 having the composition:

T-SALT SOLUTION 1 Water ml 600 NEI2HPO4 -g- 4J2 2 g 200 Thiourea g 10 2,3,5-triphenyl-ZH-tetrazolium chloride g- 10 H2O to 1 1.

pH 7.0 at 100 F.

The D of the formazan dye image replacing the silver image is measured for each of the treated elements. Table 1 shows the binder used, the formazan dye Dmax, and the image D amplification (i.e., Dye D jsilver D for each element.

TABLE 1.-SILVER HALIDE BINDER Tcrpoly- Dmsx Gelatin, mer No. Eement ing/it. (mg/ft?) W (outside invention). 144 A of invention 110 3 (34) B of invention 110 8 (34) EXAMPLE 2 Three photographic X-ray elements, X (outside our invention), C and D (both of our invention), are prepared by coating silver bromoiodide emulsions on both sides of a transparent support with emulsion X on both sides of element X, emulsion C on both sides of element C and emulsion D on both sides of element D. Each of the element layers have the same silver bromoiodide coated at 175 nag/ft. of silver and 178 mg./ft. of the binder indicated in Table 2. The elements are exposed, black-and-white processed and then treated with T salt Solution 1 as described in Example 1. The silver D fs formed by the black-and-white processing and dye D fs formed from the silver images by T-salt solution treatment are measured, and the amplification of Dmax determined for the image in each element. The results are listed in Table 2.

TABLE 2.SILVER HALIDE BINDER Tcrpoly- Dmax- Gelatin, mer No. Dye, amplifi- Eiement mgJft. (mg/it?) Dmux. cation The results show our element C with a mixture of terpolymers No. 11 and No. 3 and element D with terpolymer No. 3, respectvely, in the binder, produce substantially higher D amplification than element X containing no terpolymer in the binder.

EXAMPLE 3 Five photographic X-ray elements, Y and Z (both outside our invention), E, F and G (of our invention) are prepared. The transparent support of each element is coated on both sides with its own emulsion. Each of the emulsion layers have the same silver bromoiodide coated at 175 mg./ft. of silver and the binder indicated in Table 3. The elements are exposed and black-and-white processed as described in Example 1. After measuring the silver D fs, the elements are treated for 15 seconds at 100 F. in the T-salt Solution 2 having the composition:

2-(4,5-dimethylthiazol-2-yl)-3,5-diphenyl-2H-tetrazolium bromide g 5 The results, including D amplification, are listed in Table 3.

TABLE 3.SILVER HALIDE BINDER Terpoly- Dm,

Gelatin, mer No. Dye, amplifi- Element mgJit. (mg/ft!) Dmax. cation The results again show substantial dye image enhancement in our elements compared to the images in corresponding controls outside the invention.

EXAMPLE 4 Example 1 is repeated but with the T-salt solution at 75 F., instead of F. The results are substantially the same as obtained in Example 1. This demonstrates that our invention operates over a wide range of T-salt solution temperatures.

EXAMPLE 5 Example 1 is repeated but using T-salt solutions in which the 2,3,S-triphenyl-ZH-tetrazolium chloride of T- salt Solution 1 is replaced by 10 grams of the following T-salts:

T-salt soln.

No.: T-salt name i In each instance, the formazan dye image produced in our photographic elements containing our terpolymers in the silver halide emulsion layers is enhanced compared to the same formazan dye image formed in the respective controls.

15 EXAMPLE 6 Example 3 is repeated but using in place of 2-(4,5-dimet-hylthiazol-Z-yl)-3,5-diphenyl-2H-tetrazolium bromide used in T-salt Solution 2, 5 g. of the following T-salts:

In each instance, the formazan dye image produced in our photographic elements is substantially enhanced compared to the respective control.

EXAMPLE 7 Example 1 is repeated, using a modified T-salt Solution 1 in which the thiourea is replaced by an equimolar amount of ammonium thiocyanate. Elements A and B of our invention produce formazan dye images that are superior to the formazan dye images produced in element W outside our invention.

EXAMPLE 8 Example 1 is repeated, using a modified T-salt Solution 1 in which the thiourea is replaced by an equimolar amount of 3,6-dithia-l,8-octanediol. Our elements A and B produce formazan dye images that have D amplifications that are substantially higher than obtained with formazan dye image in element W.

This invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

We claim:

1. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder layer with a formazan dye image, wherein said metal image reduces a tetrazolium salt to form said formazan dye and metal complexing ligand forms a metal complex, the improvement wherein said replacement of said metal image with said formazan dye image is conducted in a hydrophilic colloid binder layer containing at least one terpolymer which contains at least one of the monomers represented by the formula:

where R is hydrogen, alkyl or where R is alkylene and X is aliphatic acyl or cyano and R is alkyl, cycloalkyl, aryl or where R and X are as defined, provided that one and only one of R and R is always 2. The process of claim 1 in which said binder comprises gelatin containing in the range of from about 1% to about 85% of said terpolymer.

3. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder layer with a formazan dye image, wherein said metal image reduces a tetrazolium salt to form said formazan dye and a metal complexing ligand forms a metal complex, the improvement wherein said replacement of said metal image with said formazan dye image is conducted in a hydrophilic colloid binder layer containing at least one terpolymer of (A) at least about 50% by weight of a monomer (1) having the formula:

where R is hydrogen or methyl and R is alkyl, (B) about 3 to about 30% by weight of acrylic acid or a monomer (2) having the formula:

where R is hydrogen or alkyl, 'R has its valence bonds on diiferent carbon atoms and is a divalent hydrocarbon radical or a divalent aliphatic hydrocarbon radical in which a chain of carbon atoms joining the oxygen and sulfur atoms of the above formula is interrupted by an oxygen or sulfur atom and M is a cation, and (C) about 2 to about 20%, by weight, of a monomer (3) having the formula:

where R is hydrogen, alkyl or where R; is alkylene and X is aliphatic acyl or cyano; and R is alkyl, cycloalkyl, aryl or 0 -R 0- OHzX where R is alkylene and X is aliphatic acyl or cyano, provided that one and only one of R and R is always 0 RsO -CH2X said binder comprises gelatin containing in the range of from about 1% to about of said terpolymer.

4. The process of claim 3 in which said binder comprises gelatin containing in the range of from about 20% to about 60% of said terpolymer.

5. In the process of replacing at least a portion of a photographic silver image in a hydrophilic colloid binder layer with a formazan dye image, wherein said silver image reduces a tetrazolium salt to form said formazan dye and a metal complexing ligand forms a metal complex, the improvement wherein said replacement of said silver image with said formazan dye image is conducted in a hydrophilic colloid binder layer containing at least one terpolymer of (A) in the range of from about 50% to about 92% by weight of a monomer (1) having the formula:

where R is hydrogen or methyl and -'R is alkyl, (B) about 3 to about 30%, by weight, of acrylic acid or a monomer (2) having the formula:

0 oH2=( 3-i J-0R s0zM R2 where R is hydrogen or alkyl, R has its valence bonds on different carbon atoms and is a divalent hydrocarbon radical or a divalent aliphatic hydrocarbon radical in which a chain of carbon atoms joining the oxygen and sulfur atoms of the above formula is interrupted by an oxygen or sulfur atom and M is a cation, and (C) about 2 to about 20%, by weight, of a monomer (3) having the formula:

CHFQ--OR:

where R; is hydrogen, alkyl or 0 Re-O CH2X where R is alkylene and X is aliphatic acyl or cyano; and R is alkyl, cycloalkyl, aryl or 0 RaO-- -CHz where R is alkylene and X is aliphatic acyl or cyano, pro vided that one and only one of R and R is always 0 R O-( l-CH2X said binder comprises gelatin containing in the range of from about 1% to about 85% of said terpolymer.

6. The process of claim 5 in which said tetrazolium salt is 2,3,5-triphenyl-2H-tetrazolium chloride.

7. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder layer with a formazan dye image, wherein said metal image reduces a tetrazolium salt to form said formazan dye and a metal complexing ligand forms a metal complex the improvement wherein said replacement of said metal image with said formazan dye is conducted in a hydrophilic colloid binder layer containing at least one terpoly (alkyl acrylate-alkali metal salt of 3-sulfopr0pyl acrylateacetoacetoxyethyl methacrylate) containing in the range of from about 50% to about 92% by weight of said alkyl acrylate monomer, in the range of from about 3% to about 30% by weight of said alkali metal salt of 3- sulfopropyl acrylate monomer and in the range of from about 2% to about by weight of said acetoacetoxyethyl methacrylate monomer.

8. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder layer with a formazan dye image, wherein said metal image reduces a tetrazolium salt to form said formazan dye and a metal complexing ligand forms a metal complex, the improvement wherein said replacement of said metal image with said formazan dye is conducted in a hydrophilic colloid binder layer containing terpoly(butyl acrylate-sodium 3-sulfopropyl acrylate-acetoacetoxyethyl methacrylate), 80:10:10% by weight.

9. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder layer with a formazan dye image, wherein said metal image reduces a tetrazolium salt to form said formazan dye and a metal complexing ligand forms a metal complex, the improvement wherein said replacement of said metal image with said formazan dye is conducted in a hydrophilic colloid binder layer containing terpoly(butyl acrylate-sodium 3-sulfopropyl acrylate-acetoacetoxyethyl methacrylate), 90:3:7% by weight.

10. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder layer with a formazan dye image, wherein said metal image reduces a tetrazolium salt to form said formazan dye and a metal complexing ligand forms a metal complex, the improvement wherein said replacement of said metal image with said formazan dye is conducted in a hydrophilic colloid binder layer containing terpoly(butyl acrylate-sodium 3-sulfopropyl acrylate-acetoacetoxyethyl methacrylate), 91:5:4% by weight.

11. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder layer with a formazan dye image, wherein said metal image reduces a tetrazolium salt to form said formazan dye and a metal complexing ligand forms a metal complex, the improvement wherein said replacement of said metal image with said formazan dye is conducted in a hydrophilic colloid binder layer containing terpoly(methyl acrylate-sodium 3-sulfopropyl acrylate-acetoacetoxyethyl methacrylate), :10:10% by weight.

12. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder layer with a formazan dye image, wherein said metal image reduces a tetrazolium salt to form said formazan dye and a metal complexing ligand forms a metal complex, the improvement wherein said replacement of said metal image with said formazan dye is conducted in a hydrophilic colloid binder layer containing terpoly(methyl acrylate-sodium 3-sulfopropyl acrylate-acetoacetoxyethyl methacrylate), 89:5 :6% by weight.

13. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder layer with a formazan dye image, wherein said metal image reduces a tetrazolium salt to form said formazan dye and a metal complexing ligand forms a metal complex, the improvement wherein said replacement of said metal image with said formazan dye is conducted in a hydrophilic colloid binder layer containing terpoly(methyl acrylate-sodium 3-sulfopropyl acrylateacetoacetoxyethyl methacrylate), 92:6:2% by weight.

14. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder layer with a formazan dye image, wherein said metal image reduces a tetrazolium salt to form said formazan dye and a metal complexing ligand forms a metal complex, the improvement wherein said replacement of said metal image with said formazan dye is conducted in a hydrophilic colloid binder layer containing at least one terpoly(alkyl acrylate-acrylic acid-acetoacetoxyethyl methacrylate) containing in the range of from about 50% to about 92% by weight of said alkyl acrylate monomer, in the range of from about 3% to about 30% by weight of said acrylic acid monomer and in the range of from about 2% to about 20% by weight of said acetoacetoxyethyl methacrylate monomer.

15. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder layer with a formazan dye image, wherein said metal image reduces a tetrazolium salt to form said formazan dye and a methal complexing ligand forms a metal complex, the improvement wherein said replacement of said metal image with said formazan dye is conducted in a hydrophilic colloid binder layer containing terpoly(ethyl acrylate-acrylic acid-acetoacetoxyethyl methacrylate), 82:l0:8% by weight.

16. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder layer with a formazan dye image, wherein said metal image reduces a tetrazolium salt to form said formazan dye and a metal complexing ligand forms a metal complex, the improvement wherein said replacement of said metal image with said formazan dye is conducted in a hydrophilic colloid binder layer containing terpoly(ethyl acrylate-acrylic acid-acetoacetoxyethyl methacrylate), 72:24:4% by weight.

17. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder layer with a formazan dye image, wherein said metal image reduces a tetrazolium salt to form said formazan dye and a metal complexing ligand forms a metal complex, the improvement wherein said replacement of said metal image with said formazan dye is conducted in a hydrophilic colloid binder layer containing terpoly- (ethyl acrylate-acrylic acid-acetoacetoxyethyl methacrylate), 90:8:2% by weight.

18. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder layer with a formazan dye image, wherein said metal image reduces a tetrazolium salt to form said formazan dye and a metal complexing ligand forms a metal comimage reduces a tetrazolium salt to form said formazan plex, the improvement wherein said replacement of said dye and a metal complexing ligand forms a metal commetal image with said formazan dye is conducted in a plex, the improvement wherein said replacement of said hydrophilic colloid binder layer containing metal image with said formazan dye is conducted in a (1) a terpoly(alkyl acrylate alkali metal salt of 3- 5 hydrophilic colloid binder layer containing terpoly(butyl sulfopropyl acrylate-acetoacetoxyethyl methacrylate) acrylate-sodium 3-sulfopropyl acrylate-acetoacetoxyethylcontaining in the range of from about 50% to about methacrylate) 9l:5:4% by weight and terpoly(ethyl 92% by weight of said alkyl acrylate monomer, in the acrylate-acrylic acid-acetoacetoxyethyl methacrylate) range of from about 3% to about 30% by weight 72:24:4% by weight. of said alkali metal salt of 3-su1fop-ropy1 acrylate 10 monomer and in the range of from about 2% to References Cited about t% by weight of said acetoacetoxyethyl meth- UNITED STATES PATENTS acry a e monomer, an (2) a terpo1y(alkyl acrylate-acrylic acid-acetoacetoxygmlth 2-2 ethyl methacrylate) containing in the range of from 15 eterson 9 4 about to about 92% by weight of said alkyl acrylate monomer, in the range of from about 3% FOREIGN T N to about 30% by weight of said acrylic acid monomer 8,299 1/ 1960 Great Britain 15-2 and in the range of from about 2% to about 20% by weight of said acetoacetoxyethyl methacrylate 20 NORMAN TORCHIN Pnmary Exammel' monomer. E. C. KIMLIN, Assistant Examiner 19. In the process of replacing at least a portion of a photographic metal image in a hydrophilic colloid binder US. Cl. X.R.

layer with a formazan dye image, wherein said metal 96-84 

